U.S. Pat. No. 4,021,988, assigned to the assignee of the present invention describes a door frame construction including vertical channel frame members formed of metal. Doors using that frame construction are particularly suited for on-site construction of large sliding doors of the types used on barns and industrial buildings.
It would be desirable to reduce the weight and manufacturing cost of the vertical frame members without adversely affecting the resistance of the frame to the bending stresses commonly occurring during high wind conditions. Moreover, it would be desirable to improve the resistance of the frame pieces to rust and/or corrosion and to improve the overall appearance of the completed door.